When people were shown online details about a vacation package against a blue background, their average “best offer” was $712, but it was $684 when the information was presented against a red background, say Rajesh Bagchi of Virginia Tech and Amar Cheema of the University of Virginia. The research participants were implicitly competing against the seller to get the best deal, and exposure to red induces greater aggression. Red has the opposite effect in auctions, where greater aggression makes people willing to pay more in order to best other bidders, the researchers say.